Cupola furnace

ABSTRACT

A cupola furnace is provided with at least one tunnel extending from the combustion chamber at the bottom of the shaft, for the combustion of gases passing electrodes in the tunnel which produce arc discharge, and for conveying the combustion gases to said combustion chamber.

United States Patent (72] Inventors Vladimir Alexandrovich Grachev U1. Uritskogo, 74, Kv. 9; Anatoly Alexeevieh Cherny, U1. Tsiolkovskogo, 41, kv. 32, Lev Mikhailovich Marienbakh, Bolshaya Cberkizovskaya, 5, Korp. l, Kv. 73, Ivan Lukich Kurbatsk Ul. Volodarskogo, 74, kv. 4, PEza, U.S.S.R. [21] Appl. No. 614,311

[22] Filed Feb. 6, 1967 [45] Patented Jan. 26, 1971 [32] Priority Feb. 8, 1966 [33] U.S.S.R.

[54] CUPOLA FURNACE 4 Claims, 2 Drawing Figs.

52 u.s.c1 ..13/g; 13/31; 219/121; 266/25 [51] Int. Cl 1105b 7/10 [50] Field ofSearch 13/1,2,9, 9X, 31, 33, 34; 266/25, 24; 263/52; 219/75, 121, 121P [56] References Cited UNITED STATES PATENTS 39 11. 2 i 3i 2 215.2 3,004,137 10/1961 Karlovitz 219/75 3,338,707 8/1967 Carli et a1. 266/25(X) Primary Examiner-Bernard A. Gilheany Assistant ExaminerRoy N. Envall, Jr. Attorney-Waters, Roditi, Schwartz 84 Nissen ABSTRACT: A cupola furnace is provided with at least one tunnel extending from the combustion chamber at the bottom of the shaft, for the combustion of gases passing electrodes in the tunnel which produce arc discharge, and for conveying the combustion gases to said combustion chamber.

with two sections: a lower one for maintaining a column of charge materials and an upper one for preventing the charge from falling into the lower part of the cupola furnace shaft. The operations of melting and superheating metal are carried into effect in the cupola furnace shaft by burning a gaseous fuel in its bottom part. This cupola furnace is suitable for making molten metal heated to a temperature sufficient for casting thin-walled parts. The production capacity of the gas cupola furnace is found thereby to be higher than that of a coke cupola furnace of the same size. As to its design, it is more simple and occupies a smaller floor space.

Sometimes, however, the cupola furnace is required to melt iron heated to a higher temperature as compared with that usually obtained, or to melt therein a charge containing a larger amount of oxides. In this case, it becomes necessary to create a reducing atmosphere. This is impracticable in an ordinary gas cupola furnace.

An object of the present invention is to improve the design of said gas cupola furnace.

Other objects and advantages of the present invention will become more fully apparent from a consideration of the following description thereof.

The principal object of the invention is to provide a cupola furnace, enabling an increase in the temperature of the molten metal and to obtain a reducing atmosphere in the cupola furnace.

This object is achieved by the provision of utilizing electric power and gaseous fuel, simultaneously as a source of heat for melting and superheating the metal.

In conformity with the present invention, the electric power may be best utilized by creating an electric arc discharge in a stream of gas being burned.

According to the invention, the cupola furnace is provided with a least one tunnel for burning the gaseous fuel, wherein there are provided electrodes for creating an arc discharge.

The cupola furnace'may have one electrode in the form of a ring, while the other electrode is made in the form of a rod which can be moved until it is in contact with the annular electrode.

The nature of the present invention will be come more fully apparent from a consideration of the following description of an exemplary embodiment of the cupola furnace according to the invention, taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a longitudinal section of the cupola furnace, according to the present invention; and

FIG. 2 is a cross-sectional view on enlarged scale, taken along line 11-" of FIG. 1.

The shaft of the cupola furnace is provided with two sections, viz lower one 1 (FIG. 1) for maintaining the column of charge materials and upper one 2 for preventing the charge from falling into the lower part of the cupola furnace shaft, i.e., the chamber for superheating the molten metal. The sections disposed in the middle part of the cupola furnace shaft are provided with pipes 3 and 4 intended for effecting cooling with water. A hearth 5, having a depression in the form of a well 6 for superheating the molten metal, is provided in the lower part of the shaft. The outlet holeof a tunnel 7 for buming the gas-air mixture supplied from a tuyere 8 is provided directly over the surface of molten metal in the well. FIG. 2 shows on an enlarged scale the unit functioning as the heat source. Electrodes 9 and 10 are disposed in the tunnel. The electrode 9 is made as a hollow copper toroidal member for passing cooling water supplied through a branch pipe ll.

Another electrode 10 is made of tungsten (it may be also made of graphite), and has the shape of a bent rod and is supported for movement to contact the annular electrode.

The cupola furnace operates in the following manner: a

voltage is applied to the electrodes 9 and I0, and the electrode 10 is made to approach the electrode 9 until a discharge occurs. Then it is automatically drawn off to a distance providing for the obtaining of a stable are, upon which the gaseous mixture is supplied from the tuyere into the tunnel, which mixture is thereafter ignited. Passing through the zone of arc discharge, the burning mixture is ionized, and its temperature thereby considerably increases; then it is directed into the superheating chamber on the molten metal surface. Giving off the heat to the molten metal, the gases cool to some extent, and arrive at the upper zone of the cupola furnace where they are employed for melting metal. The heat, as required for melting and superheating metal, is generated both by the combustion of gas and due to the arc discharge occurring between the electrodes (in the form of plasma). The temperature and composition of gas are controlled in wide ranges. The gas is burned in the absence of air so as to create a nonoxidizing or reducing atmosphere.

An increase in the consumption of electric power of the discharge between the electrodes is employed for increasing the temperature of gas. When burning gas with the supply of air in an amount as required for the complete combustion thereof, the consumption of electric power may be small, depending upon the temperature required and the speed of melting of the metal The temperature of metal is bound to increase drastically as a result of a direct heat transfer from the arc discharge to the molten metal surface. In this case, the fusion of the lining in the superheating chamber and in the cupola furnace shaft are reduced to some extent as a result of transferring a greater amount of heat to the molten metal. The lining of the tunnel may be water-cooled or made of highly refractory materials.

Hence, in the cupola furnace thus described, the combustion of gas is affected simultaneously with the generation of an arc discharge, which enables melting of metals having a higher melting temperature than that attainable in the ordinary coke or gas cupola furnaces. Besides, it is possible to create a high-temperature oxidizing, reducing or neutral atmosphere. All this permits to improve the quality of cast pieces.

Though the present invention is described in connection with a preferred embodiment of its realization, it is evident that there may be modifications and variants that do not depart from the idea and scope of the invention which will be readily understood by those skilled in the art.

We claim:

I. A cupola furnace for melting and superheating metal, comprising means defining a compartment for the processing 1 of said metal, a hearth in said compartment having a well for receiving molten metal, means providing at least one tunnel extending into said compartment towards said well for the combustion of a gaseous fuel, and electrodes in said tunnel for creating arc discharges to generate heat and to burn said fuel, said tunnel guiding the heat toward the molten metal in the well.

2. A cupola furnace according to claim 1, wherein one electrode is made in the form of a ring, and the other has the shape of a rod encircled by said ring and is capable of moving toward and away from said annular electrode.

3. A cupola furnace according to claim 1, wherein the first said means comprises first and second connected sections defining a shaft constituting at least part of said compartment, said tunnel extending obliquely downwards to said shaft at the bottom thereof.

4. A cupola furnace according to claim 3 comprising a tuyere opening into said tunnel at an end thereof remote from said shaft. 

1. A cupola furnace for melting and superheating metal, comprising means defining a compartment for the processing of said metal, a hearth in said compartment having a well for receiving molten metal, mEans providing at least one tunnel extending into said compartment towards said well for the combustion of a gaseous fuel, and electrodes in said tunnel for creating arc discharges to generate heat and to burn said fuel, said tunnel guiding the heat toward the molten metal in the well.
 2. A cupola furnace according to claim 1, wherein one electrode is made in the form of a ring, and the other has the shape of a rod encircled by said ring and is capable of moving toward and away from said annular electrode.
 3. A cupola furnace according to claim 1, wherein the first said means comprises first and second connected sections defining a shaft constituting at least part of said compartment, said tunnel extending obliquely downwards to said shaft at the bottom thereof.
 4. A cupola furnace according to claim 3 comprising a tuyere opening into said tunnel at an end thereof remote from said shaft. 